This invention relates to the fabrication of components, and, more particularly, to fabrication by controlled deposition of layers of the constituents.
Improvements in manufacturing technology and materials are the keys to increased performance and reduced cost for many articles. As an example, continuing and often interrelated improvements in processes and materials have resulted in major increases in the performance of aircraft gas turbine engines.
An aircraft gas turbine or jet engine draws in and compresses air with an axial flow compressor, mixes the compressed air with fuel, burns the mixture, and expels the combustion product through an axial flow turbine that powers the compressor. The compressor includes a disk with blades projecting from its periphery. The disk turns rapidly on a shaft, and the curved blades draw in and compress air in somewhat the same manner as an electric fan.
In current manufacturing practice, the compressor is made by forging the compressor disk as a single piece with slots at the periphery. The compressor blades are individually cast or forged to shape with a root section termed a "dovetail" that fits into the slots in the disk. Assembly is completed by sliding the dovetail sections of the blades into the slots in the disk. If a blade does not fit properly, fails or is damaged during service, it may be readily replaced by reversing the assembly procedure to remove the blade, and providing a new blade.
More recently, it has been proposed to form the blades integrally with the disk, in a combination termed a "blisk". The blisk approach to manufacturing offers the potential for increased performance through reduced weight. Such an article can be cast or forged as a large disk with an excess of metal at the periphery. The blades are then machined from the excess metal, integrally attached to the disk. The final product is expensive to produce, as it requires extensive high-precision machining operations. An error in machining even one of the blades may result in rejection and scrapping of the entire blisk.
Replacement or repair of a damaged blade portion of the blisk presents a difficult problem with this manufacturing approach. If all or a portion of a blade breaks off due to ingested foreign objects during operation, for example, the blisk becomes unbalanced. There is no method presently known to repair the damaged blade in a manner that does not result in reduced performance, and there is a need for such an approach. Desirably, such an approach would be utilized in manufacturing the blisk to reduce its cost. The present invention fulfills this need, and further provides related advantages.